Hydroelectricity's electricity generated by hydropower, for example, the production of power through use of the gravitational force of falling or flowing water. It's the most widely used form of renewable energy. Once a hydroelectric complex's constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide than fossil fuel powered energy plants. Worldwide, hydroelectricity supplied an estimated 816 GWe in 2005. This was approxim… (More on Hydroelectric)